The present invention relates to a technique for delivering particulate material to a gas stream. More particularly, the invention can relate to a method and apparatus for delivering particulate superabsorbent material into a moving air stream which transports the particulate material to a selected location.
Conventional production techniques have directed measured amounts of particulate material into a moving air stream to transport the particulate material through various processes and equipment. For example, absorbent articles and structures, such as absorbent pads and absorbent cores, have been formed by employing various techniques, such as wet forming techniques, and air laying techniques. Additionally, selected amounts of superabsorbent particles have been transported through conventional processes and equipment by employing moving air streams.
Conventional airlaying techniques have, for example, have employed a conveying air stream to transport particulate material from a supply reservoir, through a transport conduit and into a forming chamber. The moving air stream has been employed to inject the selected particles into the forming chamber. A foraminous forming surface, such as a forming screen, has been transported through the forming chamber, and fibrous materials, such as fibers of absorbent cellulose, have also been introduced into the forming chamber. Additionally, a vacuum source has been employed to draw a formation air flow through the forming surface. The formation air flow entrains the fibers and particulate material for deposition onto the moving forming surface. In particular systems, a nozzle has been employed to deliver and direct the particulate material into the forming chamber, and the particles have been composed of superabsorbent material.
Such conventional techniques, however, have not been sufficiently able to reliably and consistently deliver desired amounts of the particulate material into the appointed stream of moving gas for further transport. For example, particular production arrangements have desired a substantially continuous delivery of particles into a moving air stream, and the conventional delivery techniques have provided an excessive variation in the amount of particles being delivered into the moving air stream. The amount of particles being transported at a particular time has experienced undesired perturbations, and within a series of final manufactured articles, there have been undesired changes in the amount of the particulate material contained in each article. The variations in the amounts of delivered particles have worsened when the speed of the moving, transport air stream has been increased to deliver the particulate material at higher rates. As a result, there has been a continued need for improved methods and apparatus which can more reliably and more consistently deliver the particulate material into the moving gas stream.
The present invention provides a distinctive method and apparatus for directing particulate material into a moving gas stream. Generally stated, the process of the invention includes a delivering of the particulate material from a particulate reservoir along a delivery direction into a housing having a housing axis. A housing gas flow is introduced into the housing through at least one entry gas port that has been provided in the housing. The housing gas flow is arranged to combine with the particulate material that is delivered from the particulate reservoir. In a particular aspect, a swirling motion can be imparted to the housing gas flow, and the swirling motion can have at least a rotational component of movement which is directed substantially circumferentially about the housing axis.
The apparatus of the invention can include a housing having a housing axis, and an inlet conduit for delivering the particulate material from a particulate reservoir along a delivery direction into the housing. The housing has at least one gas entry port for introducing a housing gas flow into the housing. The housing gas flow is arranged to combine with the articulate material that is delivered from the particulate reservoir, and in a particular aspect, the at least one gas entry port can be configured to impart a swirling motion to the housing gas flow. The swirling motion can have at least a rotational component of movement which is directed substantially circumferentially about the housing axis.
In another aspect, the apparatus and process of the invention can further include a regulating of a rate of delivery of the particulate material from the particulate reservoir. In a further aspect, the apparatus and process can include a measuring of a weight of particulate material which is delivered from the particulate reservoir. Still another aspect of the apparatus and process can include an incorporating of a plurality of entry ports into the housing. In still other aspects, the entry ports can be provided by a plurality of control vanes or louvers. Desirably, the louvers can be configured in an array which is distributed around the housing axis, and in particular aspects, the control louvers can be arranged with a selected deflection angle.
In its various aspects and configurations, the present invention can advantageously provide an effective and cost efficient technique for forming a desired distribution or concentration of particulate and fibrous material within an absorbent article. The technique of the invention can, for example, provide a more reliable and more consistent delivery of desired amounts of particulate material into the appointed stream of moving gas for further transport. In particular aspects, the technique of the invention can substantially continuously delivery the particles into the moving air stream without excessive variation, and the amount of particles being transported in the moving gas stream at a particular time can have fewer undesired perturbations. The invention can be less susceptible to an undesired clumping of the particulate material. Additionally, the technique of the invention can reduce turbulence within the delivery system, and can reduce an undesired percolating of the particles. Within a series of final articles that have been manufactured by employing the technique of the invention, there can be fewer undesired changes in the amount of the particulate material contained in each article. As a result, the technique of the invention can better produce an absorbent article having improved absorbent performance, and can better produce an article having an improved combination of liquid uptake, liquid distribution, absorbent capacity, and leakage resistance.